Reijo Lehtiniemi

Significance of Nanotechnology for Future Wireless Devices and Communications

This paper reviews the expected wide and profound impact of nanotechnology for future wireless devices and communication technologies.

A Microfabricated Nebulizer for Liquid Vaporization in Chemical Analysis

A miniaturized nebulizer chip for vaporization of liquid samples for mass spectrometry has been designed, fabricated, and characterized for fluidic and thermal performance. Silicon/glass chip has a liquid sample channel placed centrally between symmetric nebulizer gas channels. The liquid sample is nebulized and vaporised by an integrated platinum heater. The vaporized sample exits through an etched nozzle, and is ionized by an external corona needle. The ions are analysed by a mass spectrometer. The chip has been fabricated in both anisotropically wet etched and DRIE versions in silicon, with an anodically bonded Pyrex glass cover plate. Three different fluidic inlet designs are presented, with both through-wafer and edge insert versions. The shape of the erupting gas jet has been visualized by infrared thermography by using a low-diffusivity imaging screen and high heat capacity helium as a test gas. Dimensions of the jets thermal footprint on the screen show that the jet is very narrow and confined, and this is confirmed in mass spectrometry results. This confined jet supplies the sample to the ionization region near corona tip, enabling efficient use of very small sample amounts and submicroliter flows.1591

Infrared thermography in electronics applications

Thermal engineering of electronics products has become more essential, mainly because of increasing power densities due to the past rate of miniaturization at all assembly levels. One tool, which facilitates this challenging work, is infrared (IR) thermography. With an IR camera, it is often quite easy to quickly inspect an electronic device, or usually printed circuit board (PCB), by detecting and locating possible hot spots. However, due to the relative ease of use of modern IR cameras equipped with diverse special functions, it is also rather easy to make serious misinterpretations. Typical pitfalls that arise in electronics applications include considerable emissivity variations, for instance on common PCBs and the sometimes-drastic changes of operation conditions when the device under test is removed from its operational environment to allow imaging. In this paper, these pitfalls, their effects, and the feasibility of possible remedies are discussed.

Thermal inspection of solder quality of electronic components

Solder quality of two ball grid array electronic components were studied by using a photothermal inspection technique. In order to introduce artificial defects into the components, columns of soldering joint balls were removed between the electronic component and the printed circuit board. From one of the components, the copper heat slug was also removed to enhance the possibilities for detecting the defects. The components were heated with laser light, and their surface temperatures were monitored with an infrared camera. After heating the component for 1.5 seconds, the defects were resolved, if the plastic covering was removed. In the case of the second component with intact plastic covering, the defects under the component were not resolved. The defects were not visible through the printed circuit board either.

Bibliography of the application of infrared thermography to electronics

Abstract not available.